Improvement in bit-stocks



A UNITED STA-TESPATEN'I' OFFICE..

ROBERT D. O. SMITH, OF WASHINGTON, DISTRICT OF COLUMBIA.

IMPROVEMENT IN. BIT-STOCKS.

Specification forming part of Letters Patent N0. 82,041, dated September 8,1868.

To all 'whom it may concern: A

Beit known that I, ROBERT I). O. SMITH, of Washington, in the county of Washington and District of Columbia, have invented' a new and useful Improvement in Bit-Stocks and I do hereby declare the following to be a full, clear, and exact description of the same,

jaws, Sac.; Fig. 6, modied forms of bit-head.

In the manufacture of bits it has not been customary to make the surfaces ofthe head either uniform as to plane, nor at equal ,angles with the axis of the bit itself; and as the head is required to fit accurately the socket in the head of the bit-stock, to insure either accuracy of centering or convenient steadiness, it has hitherto been, and still is, to a great extent necessary to specially fit the head of every bit to the socket of the particular stock with which it should be used. This is a work requiring considerable skill and labor, and has called forth the invention of various devices capable of holding the bit-head firmly without previous fitting; but as the bit-heads have never been manufactured so as to be true as regards the axis of the bit, i. e., forming equal angles thereto, it follows that none of these devices have truly centered the bit at the same time that the head has been firmly held.

By the term truly centered77 I mean to indicate that condition only where the axis of the bit coincides with the axis of the stock. This condition is highly desirable, and, for accurate performance, absolutely necessary, but can only be attained by reducing the planes of the head to equal angles to the axis of the bit, or by seizing and holding the bit independent of the head.

This latter method is the gist of my invention, which therefore consists in certain jaws or their equivalents, constructed so that they shall be enabled to seize and hold the bit by the cylindrical portion thereof in front of the head, said cylindrical surface being always concentric to the axis of the bit.

Having now set forth the nature and scope of my invention, I will particularly describe one of the various ways in which it may be carried into effect; but in describing only one set of devices for effecting the purpose of my invention, I do not wish to be understood as limiting myself to those special devices, because the same principles of operation will be necessarily present in any other device which is capable of the same performance, while the details of construction may be greatly varied.

A is a portion of the bit-stock, and B is the head, containing the jaws or other holding mechanism. The head B is cylindrical, and has a male screw cut upon its surface. It is also divided by a longitudinal slit, running from its end in the direction of its axis, so as to divide the head into two equal parts, and separated by about one-third of the diameter of the head. Within this slit are placed two jaws, which seize and hold the bit, and said jaws are confined and actuated by a screwsleeve, C, which is iitted to the head B, as shown. The description given in this paragraph pertains to the bit-stock known as the Barber bit-stock, which is adapted to my invention.

The jaws D D are fitted so as to ll the slot in the head B, and yet move freely therein. Their forward ends are accurately made with corresponding inclinations I to the axis of the bit-stock, and the lips E are made with equal accuracy, so as to be parallel with said axis when the jaws are in operative position. The inner surface I of forward end of the sleeve C is made to correspond exactly with the inclination of outer surface of the forward ends of the jaws D to the axis of the stock, and, these conditions being observed, it follows that, if the inclined surfaces of the forward ends of the jaws D be in contact with the inclined inner surface of the forward end of the sleeve C, the lips E will be parallel with each other and with the axis of the stock, and any cylindrical body held between said lips will be held truly centered.

The lips E I think it proper to make about one-half inch in length, and behind said lips recesses are filed out in the jaw to accommodate the head-0f the bit, as 4shown in Fig. 5,

though I should prefer to make said recesses much shorter and cut ofi' the end of the bithead, as shown in- Fig. 6, were it convenient to do so. The head of the bit does not rest 'against the side of the recess vat any point unless the strain upon the shaft during the operation of boring has been sufficient to par.

tially revolve it between the lips, in which case the angle of the head striking against the jaw will prevent any further revolution of the shaft of the bit within its seat.

At the inner Vends of the yjaws they abutV against the metal of the head B, and a simple pin, F, is sufficient to keep them in place as regards each other. If, however, the jaws y were permitted to rest against a plane surface,

transverse strains applied at the outer end of the bit might cause the inner en ds of the jaws.

correspondingly-shaped seat, as shown.

When the bit G is inserted between the lips E, and the sleeve C screwed down upon the jaws D, the inclined surfaces `I I/,heretofore described, come in contact, and, as the motion of the sleeve is continued, the jaws are forced to move toward each other, with the lips E always parallel until they come in contact with and firmly gripe the cylindrical surface of the lip G. When the jaws cease to move freely toward each other, they commence to bepressed in the direction of the axis of the stock, and will then be forced into the slightly conical seat in the end of the head B. When thus firmly secured, the bit G will not only be truly centered, but Vit will alsowbe maintained in that condition against any lateral strain not suicient to fracture or bend any of the parts.

.Having described my invention, what I claim as news- A bit-stock with the jaws D D, having a parallel movement, and sleeve C, or the equivalents of these parts, constructed so as to hold bit truly centered Aby seizing it by the cylindrical portion in front 4of the head thereof.

, R. D. O SMITH. Witnesses:

R. S. TURNER, J. S. BROWN. 

